Political ads often are remembered for their messages. (Think Ronald Reagan’s “Morning in America” spot.) Or for attention-grabbing images. (Think the mushroom cloud in LBJ’s “Daisy” commercial.)

Though voice-overs are less celebrated, they are no less important. If an ad is comparable to a restaurant dish — a meaty attack, a side of factoids, a catch-phrase garnish — then voice-overs are like salt.

Too much, and you notice. Too little, and you also notice. Just right? You focus on the food.

At the University of California at Los Angeles, Tim Groeling teaches a political advertising course in which students are required to produce their own spots. “It’s deceptively difficult to get a decent voice-over,” said Mr. Groeling, chairman of UCLA’s Department of Communications Studies. “That’s something my students often have trouble with. It’s amazing how bad a commercial can be with the wrong voice. It kills. Takes the audience out of the moment.

“The entire point of a commercial is to establish an emotional tone. You can’t have a really devastating commercial about casualties in Iraq and then have a happy, chipper voice or one that seems unserious.”

While political voice-over work might seem decidedly less nuanced than, say, a performance of “Hamlet,” the truth is that there is an art to proclaiming how Mitt Romney would ship your grandmother’s wheelchair to China for a few extra pennies in outsourcing profits, or how Mr. Obama’s economy is akin to “The Road Warrior,” albeit with fewer dune buggies.

According to Los Angeles-based voice actor D.C. Douglas, political voice-overs typically fall into four “reads,” each with their own verbal nuances:

Compassionate: Softer, heartfelt vibes for a kinder, gentler candidate. Vote for me, and I will build this orphanage, then personally hug every child inside.

Patriotic: Positive and prideful. A vote for me is a vote for the greatest nation on Earth. And bald eagles.

The disenchanted voter: The truck driver or small-business owner who is fed up with Mr. Inside-the-Beltway incumbent. Bitter and angry. But also weary. And maybe even pitying. Poor President Obama. We gave him a chance.

“The attack read can be close-to-the-vest ominous, or outright disdainful,” said Mr. Douglas, who has recorded ads attacking Mr. Romney and Sen. Richard G. Lugar, Indiana Republican. “With a bright pop at the end for the candidate paying for the ad.”

Speaking of attack ads, Mr. Groeling has noticed a trend of employing female voice actors for the most aggressive and negative material.

The reason?

“If they’re trying to do an especially harsh attack, a female voice can make it seem a little less harsh,” he said. “It also helps you maintain a little bit of dignity and distance from it.”

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About the Author

Patrick Hruby is an award-winning journalist who holds degrees from Georgetown and Northwestern. He also contributes to ESPN.com and The Atlantic Online, and his work has been featured in The Best American Sports Writing. Follow him on Twitter (@patrick_hruby) and contact him at PatrickHruby.net.